1. Field of the Invention
This invention relates in general to sliders for use in magnetic storage devices, and more particularly to slider fabrication methods and slider designs that facilitate fabrication and even more particularly to fabrication methods and slider designs which minimize damage to thin film components during lapping.
2. Description of Prior Art
A typical prior art a disk drive system 10 using magnetic recording is illustrated in FIG. 1. In operation the magnetic transducer (slider) 20 is supported by the suspension (not shown) as it flies above the rotating disk 16. The magnetic transducer 20, usually called a “head” or “slider,” is composed of elements that perform the task of writing magnetic transitions (the write head 11) and reading the magnetic transitions (the read head 12). The side of the slider that is in proximity to the disk surface is the air-bearing surface (ABS). The slider 20 is positioned over points at varying radial distances from the center of the disk 16 to read and write circular tracks (not shown). The disk 16 is attached to a spindle (not shown) driven by a spindle motor (not shown) to rotate the disk 16. The disk 16 comprises a substrate 18 on which a plurality of thin films 17 are deposited. The thin films 17 include ferromagnetic material in which the write head 11 records the magnetic transitions in which information is encoded.
During the fabrication process the materials and structures for the ABS conventionally extend beyond the ABS. The material below the ABS plane is removed by lapping to achieve precise control of the length of the sensor 13 (which is called the “stripe height”). The uncertainty of the saw plane placement causes variations in the stripe height which are on the order of microns and which would lead to unacceptable variations in magnetic performance if not corrected. Lapping is the process used in the prior art to achieve much tighter stripe height control in the nanometer range.
In the typical process of fabricating thin film magnetic transducers, a large number of transducers are formed simultaneously on a wafer. After the basic structures are formed the wafer may be sawed into quadrants, rows or individual transducers. Further processing may occur at any or all of these stages. Although sawing has been the typical method for separating the wafers into individual sliders, recently reactive ion etching (RIE) or deep reactive ion etching (DRIE) with a flourine containing plasma has been used. The surfaces of the sliders perpendicular to the surface of the wafer that are exposed when the wafers are cut form the air bearing surface (ABS) of the slider.
After lapping, features typically called “rails” are formed on the ABS of the slider. The rails have traditionally been used to determine the aerodynamics of the slider and serve as the contact area should the transducer come in contact with the media either while rotating or when stationary.
Sliders may be lapped in rows, but it may be advantageous to have the individual sliders cut out prior to lapping. Even though the sliders have been separated, it is possible to lap several at one time by attaching them to carrier. The time required to lap sliders is a significant element in the cost of manufacturing; therefore, there is a need to improve production efficiency by reducing lapping time, and achieve an ABS surface with a greater control of flatness parameters.
As the slider body is made of rather hard material, such as alumina oxide (Al2O3) and titanium carbide (TiC), diamond abrasives are used to remove slider material in a precision manner. These diamond abrasives also generate high stresses in the sensor material during lapping that lead to degraded sensor outputs. It has been discovered that the lapping process damages the structure of the ferromagnetic hard-bias material at the surface so that inconsistent signal amplitudes and low yields are obtained. One method that has been shown to be effective in reducing lapping-induced damages is to embed the sensor away from the lapping surface.
FIGS. 2A-C will be used to illustrate aspects of an existing fabrication process for heads with embedded sensors. A large number of identical heads 20 are produced on each wafer 30. As shown the head is partially completed with the read sensor only. The phase of the process in which the sensor layer structure is deposited will be called “K3”. The phase of the process which forms the hard-bias structure and defines the sensor width is also known as the “K5” stage of the process. The “K6” stage defines the lead stitch. The layering of the sensor follows the sequence of seed layer, K3, K5 and K6. After the layer stack for the sensor is deposited on the wafer, the K3 mask is laid over the sensor layer to pattern the sensor material into shape 31, shown in FIG. 2A, which defines the sensor stripe height along the longitudinal direction. Also formed at this step is a lapping gap 32 which is located along the eventual ABS line in front of the final sensor. The lapping gap 32 is filled with alumina. Following the K3 step, a K5 mask defines the shape and location of the hard-bias/lead structure 33 to define the width of the sensor 13 as shown in FIG. 2B. The hard-bias/lead structures 33L, 33R extend below the ABS in the longitudinal direction closer to lapping start line. A K6 mask is deposited over the K5-defined region to make lead stitches 34L, 34R. The remaining portion of the lapping gap 32A separates the sensor from an in-line lapping guide (ILG) which is made of the same material as the sensor and is electrically connected with the sensor in parallel between the leads.
FIG. 2C is section of the head 20 of FIG. 2A taken along line M perpendicular to the surface of the wafer. The seed layer 35 for the hard-bias/lead material 33 is the lowest layer shown.
The electrical resistance between the leads is initially the parallel combination of the resistances of the sensor and the in-line lapping guide (ILG). Lapping starts at a distance far away from the sensor structure proceeds in the longitudinal direction eventually ends at the lower end of the sensor as indicated in FIG. 2B. The fabrication process for embedded sensor has been successful in reducing damage to the sensor during lapping. However, the hard-bias (HB) material 33 is still subjected to lapping damage.
Methods for reducing the damage to the hard-bias material during lapping are needed.